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The Merits of a Basic Fitting Pattern

Slopers help simplify the fitting process.
Slopers help simplify the fitting process.

Slopers help simplify the fitting process.

The chief use of the sloper is in flat-pattern design, where the idea is that every pattern properly made from it will fit the figure the sloper fits. But having such an accurate, tangible record of your own shape can be a powerful fitting tool for existing patterns, as well. After all, if you have a sloper that fits, you've already solved your most important and most complex fitting problems. Why should you have to re-solve these problems each time you alter a pattern?

Your sloper is a two-dimensional dress form
I think of a sloper as a flat dress form, cut into front and back pieces. Lay your pattern on your "flat form," and you can see immediately whether the pattern will fit you because you can see how and where it fits the sloper, and where it doesn't. You'll almost certainly have to redistribute the sloper's dart shaping to line up with the pattern's (see What you need to know about pivoting darts below), but once that's done, it's easy to see the variance between the two shapes, even if you don't yet know how to fix it.

What you need to know about pivoting darts

Darts reduce width and length wherever you don't need it (at the sides of the bust or at the waist, for example), after you've provided the extra length required to fit across a "bump" such as bust, tummy, rear, hip, or shoulder blade. The accumulated size (measured by the angle of each dart opening) of all the darts pointing to a single bump represents the total extra width and length that bump requires for coverage. This amount is called "dart control," and in many slopers it's gathered into one big dart for each bump, as shown in drawing at far left below.

Fortunately, you can divide that one dart into two or more smaller darts without changing the total dart control, as long as their combined angles equal the total dart-control angle. Further, the position of the darts doesn't matter. Provided they all point toward the apex of the bump, the dart legs can be pivoted to end in any surrounding seam, as in the examples of altered slopers above, all of which have the same amount of dart control. In patterns, all or part of the total dart control can also be taken up in gathers, pleats, or ease at any surrounding seam, or left unstitched. The unstitched portions can also be pivoted around the bump, resulting in longer seams (and loose wrinkles) at shoulder, armscye, side, or waist, wherever the designer positions it.

Finally, dart control in a sloper extends to the apex of the bump it fits (for example, a bodice sloper's bust point), which makes pivoting easy. When converted to garment darts, the dart's point is shifted from the apex by at least 1/2 in. to smooth the fabric at the apex.
Helpful hints
To pivot darts, trace the sloper onto tissue paper, then adjust the tissue copy. Slash from the seam edge where you want to position the new dart to the dart apex, leaving a small paper hinge at the apex. Pivot the existing dart closed until the new dart opens up sufficiently. Notice how pivoting changes the angle of the sloper side seam, relative to the center front.
Comparing sloper and pattern

When you lay your sloper over any commercial pattern, it's difficult to see the relationship between them until the dart control on the sloper has been divided and pivoted to match the way it was positioned on the garment by the designer. After aligning the front and back centers on your pattern and sloper, the next step is to pivot the control so the side seams are parallel (but not necessarily aligned). But where to put the new dart(s)?

Obviously, if the pattern has any visible darts or gathers, slash your sloper tracing parallel to them but pointing to its apex, then distribute as much control to that section of the sloper as you need to align the side seams. If you can't see the dart control, it's been left unstitched, so look for lengthened shoulders and armscyes, unshaped waists and/or side seams, and (on jackets) eased roll lines, all common places for unstitched dart control. These features are also clues that some control has been positioned here, even if there's a visible dart elsewhere in the pattern.

In either case, slash and pivot your sloper tracing (as described in the drawings above) in the unstitched, dart-controlled areas just described, as you would for visible darts, until the side seams are parallel. Even if your dart-control total is different from the pattern's, as long as you've distributed yours in approximately the same directions away from the apex, you're ready to match slopers when the sides are parallel, as in Step 2 and Step 3.

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Comments (10)

catstexas catstexas writes: I wish Threads would encourage THE BIG 4 to do just this:

'ideal world in which every pattern comes with an outline of the sloper it evolved from drawn right on the pattern, aligned at center back and shoulders as described in the "2-D dress-form" example above"

Thanks for an enlightening article; I learned a lot.

Posted: 4:07 pm on November 18th

MollieJ MollieJ writes: Since it is described pretty well I got the idea, but I think a video would be extremely useful to beginners.
Posted: 6:04 am on August 10th

user-3220369 user-3220369 writes: I don't always appreciate all the help my computer gives me.....I meant sloper not slower!
Posted: 5:06 pm on December 30th

user-3220369 user-3220369 writes: Great article . I am copying it so I can have it handy all the time. I understand the concept and feel like I had an epiphany and really finally realize how to use my slower. Thank you
Posted: 5:04 pm on December 30th

tzipi tzipi writes: This is one of the most excellent articles I have ever read. I knew the concept of using a sloper but never knew how to do it. Excellent. Thank you
Posted: 9:22 pm on October 1st

KathySews KathySews writes: This is interesting and needed. I have been shown how to make a sloper but never how to use it. I do agree with Seraphim, I did not follow the part where the sloper was being manipulated. I need a video of someone adjusting a pattern to her sloper.
Posted: 9:59 am on April 20th

hvnlyhost hvnlyhost writes: I love all of the people that know more than I do about sewing and pattern making, you truly help to stretch me even further in the sewing field. Loving it...THANKS BUNCHES!!

Posted: 12:51 pm on November 7th

Seraphim Seraphim writes: I found this article very helpful. My daughter sews a lot of custom work and she measured and created a sloper for me. I was on my own to figure how to use it to fit other patterns.
I did get confused by the middle section when I was seeing the sloper being manipulated to fit the pattern, it didn't seem to make sense.

Posted: 12:07 pm on January 28th

prodileida prodileida writes: hola gracias por este espacio tan bello donde podemos ayudarnos necesito hacer un vestido imperio de novia y quiero ver algunos patrones gracias

Posted: 11:13 am on November 20th

celticstitcher celticstitcher writes: thanks for this, its really helpful, and just what I was looking for
Posted: 4:54 am on July 19th

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